STRANGEBUTTRUE- Bonfire-building: Get yuks for doing with 'water'

Q.Every year a 4-H Camp Whitewood had a Backward Day. When a counselor returned and announced that he would start the bonfire that night with water, catcalls ensued. He volunteered to drink some and did this to wild applause, then poured some on the bottom of the woodpile and walked away. To the crowd's astonishment, the fire ignited. Everyone said it had to be magic. How else could he do that? –D. Slezak

A. His trick was to pre-build the bonfire with potassium permanganate at the bottom, under the paper and kindling. He was actually drinking plain old glycerine, which reacted to start the fire. (Glycerine in sufficient quantity is a laxative.) Worse than catcalls ensued when he later admitted the hoax.

Q.Take a U.S. $20 bill and look at the "20" in the front lower right corner. What color is it, and how does this change when you tilt the bill and look at the number obliquely? What's behind this "colorful" subtlety? –A. Jackson

A. Such a variable tint results from color-shifting inks, designed to thwart counterfeiters who use copy machines to make passable replicas of certain bills, says Jearl Walker in The Flying Circus of Physics.

A copier can duplicate color from only one perspective and so cannot duplicate the subtle color-shifting in a genuine bill where the "20" first appears red or red-yellow, then green when viewed obliquely. Governments worldwide scurry to stay ahead of counterfeiters who use the latest technology to duplicate paper currencies. Other anti-counterfeiting measures are security threads and special water marks (both visible if the currency is held up to the light) and microprinting (consisting of dots too small to be reproduced by a scanner).

Q.How strongly does the Sun tug on the Earth from its perch in space 93,000,000 miles away? –N. Armstrong

A. It tugs not at all from that distance– as Albert Einstein understood and corrected Isaac Newton's theory of gravity– but rather it warps the very fabric of space (and time) right in our neighborhood.

Imagine the bending of a rubber sheet caused by a grapefruit sitting on it, the bend reaching all the way out to a distant marble that rolls along a curve in the sheet. The marble is the Earth following a circular warp in space around the Sun (grapefruit).

Thus we move not at Star Trek's warp speed but along a warped-space trajectory. And as you might suppose, even your body's mass warps the space around you, though by a minuscule amount to be sure.

Q.Try to picture the prodigious sum of the recent U.S. $800 billion bailout. One way is to imagine spending a dollar every second for over 20,000 years, or 200+ centuries! What's a more life-affirming way? –B. Obama

A. You could put $800 billion in the context of today's species extinction crisis, suggests Jennifer Sills in Science magazine. There are currently an estimated 10 million species populating the Earth. To ward against extinctions, we could equitably award $80,000 to each and every species from our $800 billion cash injection.

Imagine the 43 species of ants from E. O. Wilson's single leguminous tree in Peru pooling their resources to buy about 150,000 hectares of Amazonian forest, thus helping ensure against their disappearance. Next might be hundreds of species of tree beetles, commanding some 570,000 hectares; even $80,000 should be enough to save the few remaining jellyfish trees.

The endangered Indonesian "Pakis ata" fern would also benefit greatly, and $800,000 would go a long way in securing the future of the 10 endangered British insects recently featured on Royal Mail stamps.

On the other hand, species that are doing just fine could bank their share of the funds, including roughly 7.5 million species not considered at risk (totaling $600 billion), hedging their bets against some future need.

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Send Strange questions to brothers Bill and Rich at strangetrue@cs.com.